Large corpora such as the British National Corpus and the COBUILD Corpus and Collocations Sampler are now accessible, free of charge, online and can be usefully incorporated into a process writing approach to help develop students' writing skills. This article aims to familiarize readers with these resources and to show how they can be usefully exploited in the redrafting stages of writing to both minimize the teachers' workload and encourage greater cognitive processing of errors. An exploratory investigation comparing the use of these two online corpora in Japanese university writing classes is then described. This suggests that the participants in the study were able to significantly improve the naturalness of their writing after only a 90-minute training session and that the majority of students found these online resources beneficial, although there was a marked preference for the COBUILD Corpus and Collocations Sampler.